Anything including games and obscure software
Now, I'm assuming that by "commercial" you mean "for-pay" with no implications regarding Free/Non-Free.
The Canonical Store sells Parallels and PowerDVD. There are Linux versions of Quake and Doom as well.
The Humble Indie Bundle is a commercial collection of games that was sold as "pay what you want". The games are available for puchase independently now.
there are not some, but A LOT of commercial apps for linux, check http://lin-app.com/ :)